Stack temperature actuated control device



April' 18, 1933. M, E. HENNING STACK TEMPERATURE AGTUATED CONTROL DEVICE 2 Shets-Sheet 1 Filed April 14, 1930 April 1933- M. E. HENNING 1,904,310

STACK TEMPERATURE ACTUATED CONTROL DEVICE Filed April 14, 1930 2 Sheets-Sheet 2 SUPPLY Aj/ 7/ W flaring;

Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE MALCOLM E. HENNING, OF DES MOINES, IOWA, ASSIGNOR TO PENN ELECTRIC SWITCH I 00., or was uomns, IOWA,

A CORPORATION OF IOWA Application filed April 14,

The object of my invention is to provide a stack temperature actuated control device which is simple, durable and comparatively inexpensive to manufacture.

A further object of my invention is to provide a control device consisting of a switch unit and a stack temperature actuated thermostatic power unit interconnected for operation of the switch unit from the power unit.

Another object is to provide in a switch unit a main switch and an auxiliary switch, a thermostatic bar being provided for maintaining the main switch in closed position and a heating coil being provided to actuate the thermostatic bar to non-maintaining position after a predetermined length of time whereby to open the main switch if heat fails to pass through a stack within a limited time.

Still a further object is to provide a stack temperature actuated control device for connection in series with an oil burner motor or the like whereby to stop operation of the motor in the event that heat fails to be generated by the burner within a specified time.

Still a further object is to provide a means to balance the thermostatic bar to prevent undesirable operation of the device as caused so by changing temperature conditions in the surrounding atmosphere.

With these and other objects in view my invention consists in the construction, ar-

rangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illhstrated in the accompanying drawings, in which:

Figure 1 is a perspective view of my stack temperature actuated control device.

Figure 2 is a front elevation of the same showing the cover removed from the switch unit and showing parts of the device broken away and other parts shown in section the device being illustrated in connection with a stack.

Figure 3 is a view similar to a portion of the lower left side of Figure -2 illustrating the parts in a different position.

1930. Serial No. 444,202.

Figure 4 is a sectional view on the line 44 of Figure 2.

Figure 5 is a sectional view on the line 55 of Figure 1.

Figure 6 is a sectional view on the line 66 of Figure 5.

Figure 7 is a sectional view on the line 77 of Figure 2.

Figure 8 is a sectional View on the line 88 of Figure 2.

Figure 9 is a sectional view on the line 99 of Figure 2.

Figure 10 is an electrical diagrammatic view of an oil burning furnace, a room thermostat, a furnace thermostat and my stack temperature actuated control device in the electric circuit of the burner motor.

Figure 11 is a diagrammatic view of the electrical connections within the control device; and

Figure 12 is a sectional view on the line 1212 of Fig. 2.

My control device includes a mounting flange 10 adapted to be secured by bolts 12 or the like to the side of a stack 14 extending from a furnace 16 to a chimney orthe like. The device can be mounted in positions other than the one illustrated on the drawings to suit any type of installation encountered. The flange 10 is provided with a sleeve 18 adapted to receive a sleeve 20 of a clutch housing 22. A switch casing 24 is secured to the housing 22 and supported thereby by means of screws 26. A set screw 28 serves to connect the sleeves 18 and 20 together.

The end of the sleeve 20 opposite the housing 22 is closed by a Web 30 (see Figure 6) on which is formed a hub 32. One end of a coiled thermostatic bar 34 is secured to a rod 36 rotatably mounted in the hub 32 and in the end of the housing 22 opposite the sleeve 20. Y

7 housing, etc. pro' erly cooled.

' tain Within the swltch casing 24 I provide an auxiliary switch arm 48 plvoted on a pivot pin 50. A leafspring 52 is secured to the switch 'arm 48 and carries a contact 54 adapted to coact with a stationary contact 56. The contact 56 is carried by a' contact plate 58 in position for the switch arm 48 to come to rest adjacent the poles of a permanent magnet 60 when the contacts 54 and 56 are engaged with each other. An operative con-' nection is provided between the rod 36 and the switch arm 48 by means of a link 62 connected with the lever 46 of the levered disk 40 and an arm 64 to which the link 62 is pivoted and which is secured to the switch arm 48 as best shown in Figure 2.

Within the switch casing'24 I provide a main switch consisting of a spring switch blade 66 carrying a contact 68 to engage ,with a contact 70 when the main switch is closed as shown in Figure 3. A resilient finger 72 extends from the switch blade for contact with a pivoted lever 74 which is adapted to be manually moved for closing the main switch by a switch button 76.

The main switch is adapted to be maintained normally in closed position by a thermostatic bar 78 having a catch 80 en aging the arm 74 when pressed inwardly y the button 76 as shown in Figure 3. This thermostatic bar is susceptible to temperature changes of the surrounding atmosphere, and to overcome this I provide a second thermostatic bar 82 connected therewith by a fitting 84 pivoted on the screw at 86. The thermostatic bars 78 and 82 are mounted in opposition to each other so that the latch 80 will remain in fixed position regardless of surrounding temperature changes. In other words, when there is a temperature change acting upon the bar 78 to move the latch 80 in one direction the same temperature change acts upon the thermostatic bar 82 to move it an equal distance in the opposite direction. Hence, it remains, in effect, fixed. A button 77' is provided to trip the latch 80 manually.

A heating coil 88 is rovided adjacent the thermostatic bar 78 w ereby after the temperature of the coil has been raised to a cergredetermined degree after a certain erio of time, the thermostatic bar 78 will e flexed to the position shown in Figure 2 for releasing the arm 74 and allowing the main switch to open. An adjustment is provided to vary the length of time required to flex the thermostatic ar 78 to such position and consists of a control knob 90 secured to a shaft 92 which is threaded as indicated at 94 into a collar 96. The collar 96 has a pair of grooves into which the free end of the thermostatic bar 82 fits whereby rotation of the knob 90 will move the collar 96 toward the right or left, as viewed in Figure 5, for consequently changing the position of the latch 80.

In Figure 11 I have illustrated the elec- I trical connect ons within the switch unit of my device and it will be seen that a lead wire a extends from a prong 98 to the main switch blade 66. A lead wire 5 extends from the contact 70, to one end of the heating coil 88 and to the auxiliary switch arm 48. A lead wire 0 extends from the other end of the heating coil 88 to a prong 100 which is electrically connected by means of a screw 102 with the contact plate 58. Thus it will be seen that the auxiliary and main switches are connected in series, with the heating coil 88 shunting the auxiliary switch.

In Figure 10 the stack temperature actuated control device is referred to by the reference character A, a furnace thermostat by the reference character B, and a room thermostat b the reference character C. It will be seen that these three control devices are connected in series with each other and in series with an oil burner motor M.

Practical operation In the operation of the control system as best illustrated in Figures 10 and 11, let us assume that the parts are in normal position as shown in Figure 11 with the main switch closed, the auxiliary switch open and the switches B and C closed and open respectively due to the fact that the stack 14 is cold and thereby maintains the switch B closed; and the room is sufliciently warm for the thermostat C to be open. When the room cools down to a predetermined degree the switch C will be closed, whereupon the'motor M will start with the current flowing through the heating coil 88 of the auxil ary control switch and through the main switch thereof. If everything has functioned properly the stack 14 will immediately heat up whereupon the contacts 54 and 56 will be closed before enough heat has been radiated from the heating coil 88 to trip the catch 80. Thereafter if the stack continues to heat the thermostatic co l 34 will be actuated further and slip the frictional connection betweenthe rod 36 and the levered disc 40.

As soon as either the control switch B or the control switch G becomes opened because of the heat of the furnace or the room rising to a predetermined degree, the motor M will stop andthe stack 14 will commence to cool down. At the beginning of this cooling operation the switch 48 will soon be opened whereupon the frictional connection will again slip until operation of the thermostatic coil 34 caused by cooling down of the stack has ceased. Thus the slippable friction connection insures that when the stack thermostat 34 begins to operate in either direction, the switch 48 will be immediately operated.

When it is desired to change the length of time for the latch 80 to unlatch because of the heat radiated from the heating coil 88 the knob 90 may be rotated in the desired direction.

In the event the control device A becomes inoperative due to excessive temperatures which sometimes occur in an overheated stack, which causes the bimetallic metal thermostatic unit 34 to melt away, I provide a means for opening the auxiliary switch arm 48 which consists of a flange 104 formed on the connector 63 interposed in the link 62. A spring 106 is interposed between the flange 104 and the casing 24 as best shown in Figure 2. The spring 106 is of insuificient strength to overcome the power imparted to the switch arm 48 by the thermostatic element 34, but is suflicient to overcome the magnetic influence of the magnet 60 on the arm 48 in the event that the thermostatic bar 34 melts and thereby becomes inoperative. The current will then flow into the heating element 88 whereupon the main switch 66 will be moved to open position by the thermostatic bar 78 releasing the catch 80 from the lever 74. In this way the circuit will be opened in the event of damage to the control device as caused by excessive stack temperatures.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention 1. In a stack temperature actuated control device, athermostatic power unit, an auxiliary switch operatively connected therewith, a main switch in ser1es with said auxiliar switch, a heating coil shunting said auxi iary switch, a thermostatic bar adjacent said heatin coil and o eratively connected with sai main switdh for opening the same upon the thermostatic bar being moved by a predetermined rise of the temperature of said heating coil and means to open said auxiliary switch if said power unit becomes inoperative.

2. In a stack temperature actuated control device, a thermostatic power unit, an auxiliary switch operativel connected therewith, a main switch in series with said auxiliary switch, a heating coil shuntin auxi iary switch, a thermostatic bar a 1acent said heating coil and o ratively connected with said main switch or o ening the same upon the thermostatic barjing moved by U a predetermined rieeof the temperature of vice to inoperative position after said power unit becomes inoperative, said power unit being capable of operating said control device against such tension.

Des Moines, Iowa, February 28, 1930.

I MALCOLM E. HENNING.

said 

